Process for preparing soap bars free of omega phase soap



United States Patent 3,523,909 PROCESS FOR PREPARING SOAP BARS FREE OF OMEGA PHASE SOAP George Rowland Bradley III, Madeira, Ohio, and Marinus Anton Hoolboom, The Hague, Netherlands, assignors to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio No Drawing. Filed Jan. 3, 1967, Ser. No. 606,592 Int. Cl. C11d 13/00, 13/18, 13/24 US. Cl. 252--370 8 Claims ABSTRACT OF THE DISCLOSURE A process for preparing soap bars substantially free of omega phase soap, comprising sequential drying and cooling steps, several of said steps involving limitations on conditions such as temperature, moisture and pressure. A specific molten soap composition is dried under pressure to a moisture content of from about 17% to about 24%. Then, the molten soap composition is cooled quickly to a temperature of from about 25 C. to about 60 C. After flakes are formed during milling, the moisture content of the flakes is further reduced to a final moisture level of from about to about 14%. The dried flakes are then formed into a soap bar by plodding and extruding.

This invention relates to soap bars. More particularly, this invention relates to a process for preparing soap bars substantially free of omega phase soap which is less soluble than a neat soap matrix.

The presence of the poorly-soluble omega phase soap in the neat soap matrix has been a recurring problem in manufacturing soap bars from molten soap compositions. The prior art processes generally comprised the steps of drying molten soap compositions to a predetermined moisture content, i.e., the moisture content of the finished bars, and then cooling and solidifying the soap compositions. When these prior art processes are utilized, small amounts of omega phase soap are formed in a primarily neat soap system. The presence of this poorly-soluble soap phase in the more easily soluble neat phase is, of course, undesirable.

Accordingly, it is an object of this invention to provide a process for preparing soap bars substantially free of omega phase soap. Another object of this invention is to provide a process which utilizes existing soap-making equipment and increases the capacity thereof to prepare soap bars which are substantially free of omega phase soap.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating the preferred embodiments of this invention, are given by way of illustration only since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art. All'parts and percentages set forth herein are by weight.

It has surprisingly been discovered, according to the present invention, that the foregoing objects are attained by a process comprising the steps of:

(1) preparing a molten soap composition consisting essentially of: (A) from about 27 to about 36% water; (B) from about 0% to about 9% unsaponified coconut fatty acid; and (C) from about 55% to about 75% anhydrous soap, said soap containing from about 15% to about 55% soap wherein the acyl chains are derived from coconut oil and from about 45% to about 85% soap wherein the acyl chains are derived from tallow,

Patented Aug. 11, 1970 the cations of said soap consisting essentially of a mixture of from about 0% to about potassium ions and from about 80% to about 100% sodium ions;

(2) drying said soap composition to a moisture level of from about 17 to about 24% by heating said soap composition to between 90 C. and 130 C. while maintaining said soap composition under a pressure of from about 25 to about 100 pounds per square inch gauge, reducing the pressure on said soap composition to from about 0 to 15 pounds per square inch gauge, thereafter exposing said soap composition to a pressure ranging from about 15 pounds per square inch gauge to about 5 pounds per square inch gauge whereby water vapor is lost from said soap composition;

(3) forming soap flakes by cooling the molten soap composition of Step 2 to a temperature of from about 25 C. to about 60 C. and milling said soap composition to a flake thickness of from about 0.005 inch to about 0.03 inch;

(4) dryin the soap flakes of Step 3 to a final moisture level of from about 5% to about 14% while maintaining said soap flakes at a temperature of from about 25 C. to about 60 C.;

(5) and thereafter plodding and extruding the soap flakes into soap bars.

In the first step of this novel process, a molten soap composition is prepared. The molten soap compositions of this invention consist essentially of (A) from about 27% to about 36% water, preferably from about 30% to about 34% water; (B) from about 0% to about 9% unsaponified coconut fatty acid; and (C) from about to about 75 anhydrous soap, preferably from to anhydrous soap. The soap composition is comprised of from about 15 to about 55 soap having acyl chains derived from coconut oil and from about 45% to about 85 soap having acyl chains derived from tallow. In a preferred embodiment of this invention, said soap composition is comprised of from about 15 to about 25% soap having acyl chains derived from coconut oil and from about to about soap having acyl chains derived from tallow.

Coconut oil and tallow are comprised of glycerides. In their hydrolyzed form, the compositions of the coconut oil and tallow which are utilized in this invention, in parts by weight, are approximately as follows:

Parts by weight The tallow can be hydrogenated to an iodine value of about 42 but hydrogenation is not necessary for proper functioning of this process. The iodine value of coconut oil is about 12; therefore, hydrogenation of the coconut oil is not practiced. In the process of this invention, it is preferred that the saponifiable material utilized herein have approximately the same composition as described above.

However, certain natural and synthetic saponifiable materials can be substituted for the above-described coconut oil and tallow. For example, palm kernel oil is the practical equivalent of coconut oil in the practice of this invention. Additionally, small amounts of vegetable or marine oil can be substituted, in part, for the tallow. Vegetable seed oils or fats, at least 50% by weight of the combined fatty acids of which are la'uric and/ or myristic acids, can be substituted, in part, for coconut oil. Many examples of these oils are given in Hilditch and Williams, The Chemical Constitution of Natural Fats, 4th edition, 1964.

Small amounts of other saponifiable materials can also be utilized in preparing the soap compositions of this in vention. For example, the following can be substituted, in part, for coconut oil and tallow; soybean oil, cottonseed, oil, corn oil, castor oil, peanut oil, linseed oil, sesame oil, oleo-oil, olive oil, whale and fish oils, stearic acid palmitic acid, myristic acid, lauric acid, capric acid, caprylic acid, oleic acid, linoleic acid, and mixtures of such acids. It is preferred, however, that coconut oil and tallow be utilized in major amounts in preparing the soap composition of this step.

In preparing the initial molten soap composition, the saponifiable materials hereinbefore enumerated are saponified with a stoichiometric amount of alkali metal hydroxide by methods well known to persons skilled in the art. As hereinbefore specified, the cations of the soap are comprised of from about 80% to about 100% of sodium ions and from to about potassium ions. Accordingly, the alkali metal hydroxide can be comprised of a mixture of potassium hydroxide and sodium hydroxide in the before-mentioned amounts.

After saponification is completed, or nearly completed, from about 0% to about 9% coconut oil fatty acids are added to the soap composition. A minor portion of the coconut oil fatty acids may be saponified; however, the bulk of these fatty acids are not saponified. If an excess of alkali metal hydroxide is utilized in saponifying the coconut oil and tallow, a corresponding stoichiometric excess of coconut oil free fatty acids can be added to the molten soap composition. This excess coconut oil free fatty acid is saponified by the excess alkali metal hydroxide in the molten soap composition. The unsaponified coconut oil free fatty acid in the molten soap composition should range from about 0% to about 9% by weight of the molten soap composition.

The soap composition, as hereinbefore mentioned, contains from about 27% to about 36% water, and in a preferred embodiment of this invention, contains from about 30% to about 34% water.

Many materials which make the product more eflfective or more attractive can be added to the molten soap composition with no detriment to this process. These materials include sodium chloride, sodium silicate, and magnesium sulfate heptahydrate in amounts of up to 8% by weight of the finished composition, and perfumes, whiteners such as titanium dioxide, bacteriostatic agents and dyes in amounts of up to about 3%.

The second step of this process involves drying the molten soap composition to a moisture content of from about 17% to about 24%, preferably from about 18% to about 22% by weight of the total soap composition. It is desirable in this step of this process to reduce the moisture content of the soap composition while maintaining it in a molten state. The molten soap can then be further cooled, dried and made into soap bars with existing soapmaking equipment as hereinafter explained.

The drying process that is preferred in this invention comprises heating the soap composition to its boiling point between 90 C. and 130 C. while maintaining the soap composition under a pressure of from about 25 to about 100 pounds per square inch gauge (p.s.i.g.). The pressure is then gradually reduced to from about 0 to about 15 p.s.i.g. As the pressure is reduced, the soap composition splits into two phases. One phase comprises the soap composition and the second phase comprises vaporous water i.e., steam, which has been vaporized from the soap composition. In most commercial, pressurized drying apparatus, e.g., a heat exchanger, the pressure drops continuously from the inlet end to the outlet end of the heat exchanger, due in part to expansion of the soap composition and vaporization of water in the soap composition.

Especially preferred apparatus for drying the soap composition to a moisture content of from about 17% to about 24% is a plate heat exchanger. A plate heat exchanger is a relatively small, inexpensive piece of equipment with excellent heat transfer characteristics. It consists of a series of parallel plates which are separated by rubber gaskets and held under compression by tie bolts. Rubber gaskets direct the flow of soap and heating medium to opposite sides of the plates. The beating medium generally utilized is pressurized steam. The steam pressures utilized herein range from about 20 to about p.s.i.g. One excellent heat exchanger of this type is manufactured by Rosenblad Corporation of Canada, Ltd. and will hereinafter be referred to as a Rosenblad heat exchanger.

The molten soap composition of Step 1 is pumped to the heat exchanger under a pressure of from about 25 to about 100 p.s.i.g. and heated within the plate heat exchanger to a temperature of from 90 C. to C. The soap enters the heat exchanger as a single phase. As it reaches its boiling point and begins to boil, the soap composition forms two phases, that is, a soap phase and a steam phase. The soap continues to boil through the remaining stages in the heat exchanger. As the soap composition proceeds through the heat exchanger, the pressure drops. At the outlet end of the heat exchanger, the pressure should be from about 0 to about 15 p.s.i.g.

After leaving the heat exchanger, the soap composition is exposed to a reduced pressure area, i.e., from about 15 p.s.i.g. to about 5 p.s.i.g. Preferably, the soap composition is merely exposed to the atmosphere upon leaving the heat exchanger. The steam flashes from the soap composition when the soap composition is exposed to these lower pressures, e.g., atmospheric pressure. The soap composition resulting from this drying step is in a molten state and has a moisture content of from about 17% to about 24%.

The third step of this invention involves forming soap flakes by quickly cooling the molten soap composition of Step 2 at a substantially constant moisture level of from about 17% to 24%, preferably from 18% to 22%, to a temperature of from about 25 C. to about 60 C., and milling said soap composition to a flake thickness of from about 0.005 inch to about 0.03 inch. Chill rolls which are presently available in nearly all soap-making operations and are Well known in the art can advantageously be utilized in this cooling and milling step. The molten soap composition is fed slowly onto the chill roll. A thin layer of molten soap, when placed in contact with the chill roll, is cooled quickly to a temperature of from about 25 C. to about 60 C. and then milled to a thickness of from about 0.005 inch to about 0.03 inch. The soap composition of Step 2 is thus solidified. A scraper blade is utilized to remove the thin solidified layer from the chill roll. This sheet is then broken into flake form.

The soap composition of Step 2 can be cooled slowly without milling and still obtain the benefits of this inven tion. However, slow cooling is ordinarily disadvantageous from a commercial standpoint because it wastes time and space.

The fourth step of this invention involves drying the soap flakes of Step 3 to a moisture content of from about 5% to about 14% while maintaining the temperature of the soap composition at from about 25 C. to about 60 C. The preferred moisture content of the finished soap flakes is from about 8% to about 12% by weight of the composition. These flakes can be dried by any conventional means. Generally, however, standard flake dryers, which are conventional equipment in most soap-making operations, and well known in the art, are utilized in this drying step.

Other conventional drying methods, for example, ordinary cabinet drying, can be utilized in the process of this invention. For other types of dryers, see Perry, Chemical Engineers Handbook, 3rd edition (1950), pages 813-874.

By utilizing the process of this invention, the capacity of existing soap-making equipment is increased. The drying process of Step 2 can be performed by an eflicient, yet relatively inexpensive, addition to existing soap-making lines. The process of Step 2 removes excess water and allows the chill rolls of Step 3 and the flake dryers of Step 4 to operate at maximum capacities without the formation of the undesirable, poorly-soluble omega phase soap.

The fifth step of this invention involves forming the soap flakes of Step 4 into soap bars. This is accomplished by plodding and extruding the milled and dried soap flakes of Step 4 into blank bar form. This fifth step is a wellknown and conventional process in the soap-making industry and is not critical to the process of this invention.

The above-described steps describe a continuous process for preparing a soap bar which is substantially free of omega phase soap. The following examples are intended to further explain and illustrate the present invention. These examples are not intended to limit the invention in any manner.

EXAMPLE I A molten soap composition is prepared having the fo1- lowing composition by weight.

Parts by wt.

Sodium soap (20% derived from coconut oil and 80% derived from tallow) 63.5 Water 32:0 Coconut oil fatty acid 4.5

The molten soap composition is pumped to a Rosenblad plate heat exchanger under a pressure of 60 p.s.i.g. and a temperature of about 82 C. Steam is introduced under a pressure of about 100 p.s.i.g. and at a temperature of about 170 C. The molten soap composition is heated in the heat exchanger to about 120 C. The soap composition boils and splits into two phases in the heat ex changera soap phase and a steam phase. The soap com position emerges from the plate heat exchanger under a gauge pressure of about 3 pounds per square inch and at a temperature of about 105 C.

The soap composition is vented to the atmosphere and water in the form of steam is immediately lost to the atmosphere. The moisture content of the resulting molten soap composition is about 22% by weight.

This molten soap composition is then dropped onto a rotating, three roll, chill roll, cooled to a temperature of 30 C. and solidified in a thin sheet of soap of about 0.01 inch thick. These thin sheets of soap are continuously scraped from the chill roll and broken into flakes.

The soap flakes from the chill roll are dried to a moisture content of 11% in a conventional flake dryer with 50 C. air. These flakes are plodded and then extruded in continuous blank bar form. This continuous bar is cut into lengths suitable for use as toilet bars. No omega phase soap is present in these bars.

When this same soap composition is, first, dried to about 14% moisture by weight, quick-chilled on the chill roll to 30 C., dried to 11% moisture, plodded and extruded as described above, poorly-soluble omega phase soap is present in the primarily neat soap bar.

It is not commercially feasible to cool and solidify the soap composition containing 30% moisture and then dry it with air at about 60 C. The process is too expensive and too time consuming to be utilized commercially.

EXAMPLE II A molten soap composition is prepared having the following composition by weight.

Parts by wt. Sodium soap (50% derived from coconut oil and 50% derived from tallow) 60.5 Potassium soap (50% derived from coconut oil and 50% derived from tallow) 4.0 Water 30.0 Coconut oil fatty acid 5.5

The molten soap composition is processed in the same manner as illustrated in Example I. The moisture content of the soap composition is about 19% after passing through the Rosenblad plate heat exchanger and being vented to the atmosphere. The soap composition is solidified in a thin sheet of about 0.017 inch on the chill roll. This sheet is broken into flakes and the flakes are then dried to a moisture content of 11%, plodded and extruded in bar form. These bars are substantially free of omega phase soap.

EXAMPLE III The process of Example I is repeated using the same soap composition of Example I except no coconut oil fatty acid is present in the soap. The results of Example III are substantially the same as the results of Example I in that the resulting bars are substantially free of omega phase soap.

The foregoing description of the invention has been presented describing certain operable and preferred embodiments. It is not intended that the invention should be so limited since variations and modifications thereof will be obvious to those skilled in the art, all of which are within the spirit and scope of this invention.

What is claimed is:

1. A process for preparing soap bars substantially free of omega phase soap comprising the steps of:

(1) preparing a molten soap composition consisting essentially of by weight: (A) from about 27% to about 36% water; (B) from about 0% to about 9% unsaponified coconut oil fatty acid; and (C) from about to about 75% anhydrous soap, said soap containing from about 15% to about 55% soap wherein the acyl chains are derived from coconut oil and about 45% to about 85% soap wherein the acyl chains are derived from tallow, the cations of said soap consisting essentially of a mixture of from about 0% to about 20% potassium ions and from about 80% to aboutl00% sodium ions;

(2) drying said soap composition to a moisture level of from about 17% to about 24% by heating said soap composition to between 90 C. and 130 C. while maintaining said soap composition under a pressure of from about 25 to about 100 pounds per square inch gauge, reducing the pressure on said soap composition to from about 0 to about 15 pounds per square inch gauge, thereafter, exposing said soap composition to a pressure ranging from about -15 pounds per square inch gauge to about 5 pounds per square inch gauge whereby Water vapor is lost from said soap composition;

(3) forming soap flakes by cooling the molten soap composition of Step 2 to a temperature of from about 25 C. to about C. and milling said soap composition to a flake thickness of from about 0.005 inch to about 0.03 inch.

(4) drying the soap flakes of Step 3 to a final moisture level of from about 5% to about 14% while maintaining said soap flakes at a temperature of from about 25 C. to about 60 C.;

(5) and thereafter plodding and extruding the soap flakes into a soap bar.

2. The process of claim 1 wherein the soap composition of Step 1 contains from about 30% to about 34% Water.

3. The process of claim 1 wherein the soap composition of Step 1 contains from about 60% to about anhydrous soap.

4. The process of claim 1 wherein the soap composition of Step 1 contains from about 15% to about 25% soap wherein the acyl chains are derived from coconut oil and from about to about soap wherein the acyl chains are derived from tallow.

5. The process of claim 1 wherein the soap composi- References Cited tion is all sodium soap.

6. The process of claim 1 wherein the soap composi- UNITED STATES PATENTS tion of Step 2 is dried to a moisture level of from about 2,724,702 11/1955 Marshall- 18% to about 22% by weight of the total composition. r 2,295,594 9/ 1942 Mills- 7. The proces of claim 1 wherein the soap composi- 3,408,299 10/1968 Henry tion of Step 4 is dried to a moisture level of from about 8% to about 12% by weight of the total composition. LEON ROSDOL Pnmary Exammer 8. The process of claim 1 wherein a plate heat ex- D, L, ALBRECHT, A i t t E i changer is utilized in Step 2 to dry the soap composition 19 of Step 1 to a moisture level of from about 17% to about US. Cl. X.R. 24% by weight of the total composition. 252108, 368 

